A multimeter of this type has been described on page 104 of the German technical journal "Elektronik", No. 25 of Dec. 16, 1983. In this multimeter the clip is a separate instrument transducer which is connected by cable to the display unit. Moreover, in EP-A No. 67 527, there is described a clip-on measuring device provided with two Hall sensors, which is designed as a one-piece measuring device with a digital measured value display and which, owing to a special opening mechanism of the clips, is particularly suitable for measuring direct currents.
Such clip-on measuring devices have found wide acceptance in the fields of electrical installation measuring engineering because they, as is well known, permit current measurements to be carried out without any opening or stripping of the conductor, hence during normal operation.
It has been noticed as a disadvantage of such clip-on measuring devices that their measuring accuracy still leaves a lot to be desired. Also, different types of clip-on measuring devices are required for d.c. and a.c. measurements, while those which are provided with Hall sensors, as shown above, can be made suitable for both d.c. and a.c. measurements. There are also known clip-on power meters to which, for power measurement, there is additionally applied the voltage which is taken off by the user.
Mostly, the accuracy of the measurement also suffers from the fact that the measured value as displayed depends on the shape of curve, and hence does not correspond to a genuine root-mean-square-value measurement.
It is the object of the invention as characterized in the claims, therefore, to further embody the previously described multimeter in such a way that it, with improved accuracy, permits the measurement of displayed current, voltage, power and frequency values which are all independent of signal shapes, with the possibilities of practical use of the multimeter still not yet being fully exhausted.